A Comparative Study of Titanium-Based Coatings Prepared by Magnetron Sputtering for Biomedical Applications

Introduction : Titanium (Ti)-based coatings are widely used to enhance the surface properties of 316L stainless steel (SS) in biomedical applications. Notably, titanium nitride (TiN) and titanium oxynitride (TiON) are considered advanced ceramics due to their exceptional technical properties. This study explores the properties of TiN and TiON coatings deposited via magnetron sputtering, with a particular focus on how substrate bias voltage influences wettability and corrosion behaviour, driven by the surface's physico-chemical traits.

Methods : A pure titanium nitride target was sputtered in a mixed gas atmosphere of argon and oxygen onto various substrates, such as stainless steel, silicon, and glass. The substrate--target distance was set to 30 mm, and the working pressure was maintained at 10^-2 Torr. A negative DC bias voltage (0V and -100V) was applied during a 30-minute deposition period. Wettability was assessed and electrochemical behaviour was evaluated in a physiological simulated solution over 12 hours of immersion in Hanks' solution

Results : Substrate bias voltage did not affect the thickness and grain size of the coatings, except for the roughness in TiN coatings, which decreased with a -100V bias. Wettability tests indicated that TiN coatings had low contact angles and better wettability, whereas TiON coatings showed high contact angles and poorer wettability. The Icorr values for TiN (0V and -100V) were significantly lower than those for 316L steel. TiON coatings demonstrated even greater corrosion resistance, significantly outperforming uncoated steel.

Conclusions : TiN and TiON coatings, applied with and without substrate bias (0V and -100V) using magnetron sputtering, were evaluated for potential biomedical applications. These coatings exhibited distinct surface characteristics, particularly in terms of contact angle, wettability, and corrosion resistance. The use of negative substrate bias voltage significantly improved corrosion properties. Based on the observed data, TiON coatings are highly appropriate for medical implants.